High density, Less-Volatile, High Heat capacity Fluid

hey
I am a college student and am looking for a liquid having the following properties at very low temperatures (probably around 100-150 K) -
1) Very high density
2) Very high temperature of vaporization
3) Less- Volatile
4) High specific heat capacity

Your terms “very”, “very”, “less” and “high” are all a bit open to interpretation.
Maybe if you told us the application you wanted it for we could make some suggestions of liquids that not only meet your requirements, but are safe, low cost and available.

Well, i read about the concept of a black body....
So, i was trying to develop a system which would absorb all the radiations falling on it.

As a perfectly black body is nearly impossible.
So, what i am planning to do is to have a fluid withing a multiple layers of thermal conductors and insulators having highly polished surface from inside.
The fluid is suppose to be at a very low temperature somewhere around 100 k or so, so that it attracts all the heat. And all the other properties that i listed in my original post are gonna facilitate in the absorption of thermal radiations.

I have attached a simple layout of the desired system....
kindly help me out with it...........

Attached Files:

Most of time, cryogenic cooling is done by low boiling liquids - they are allowed to evaporate but since they are cheap and safe, it is not a problem, it is a feature because latent heat stops them from warming.

High boiling liquids exist, like propane. But how do you want to keep them near their freezing point rather than allow them to warm to their boiling point?

Well, that's where the trick lies.
i want the fluid to have high specific heat capacity so that it requires a large amount of energy to increase its temperature.
And the boiling point should also be high as if it starts evaporating then radiation heat transfer would become dominating which i don't want.
i know i am asking for a nearly ideal fluid, but there should atleast be something like this.

Your diagram of a liquid filled container shows multiple internal reflections. If the internal surface was not polished it would absorb energy sooner and so reduce reflected energy passing back out through the window.

It does not matter which way the shiny or the matt side of an insulating sheet faces, it insulates either way. It is still better to polish both sides.

If you want the liquid to absorb all energy then presumably you will monitor it's rising temperature. At some temperature it will evaporate. Thermal radiation from the liquid will increase as the temperature of the liquid increases.

If you want to absorb all radiation passing through the window then you may as well let it evaporate the liquid and vent the gas elsewhere, the temperature will then remain constant without need for high thermal capacity. That will stabilise the rate of radiative heat loss and make for simpler flux measurements.

A perfect thermal sink is a broadband transmission line or a pipe, not a cul de sac, reflector or lake.